JP2006073047A - Method for manufacturing magnetic recording medium and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a magnetic recording medium by which degradation in quality and reduction in yield due to stress generated by thermal shrinkage of a support roll and by thermal expansion of a winding core are prevented, and to provide the magnetic recording medium. <P>SOLUTION: In the method for manufacturing the magnetic recording medium, when the support roll is formed by winding a support on the winding core, the relation of 200≥54,000/D+0.007L+10<SP>6</SP>α is satisfied, wherein the outside diameter (mm) of the winding core, the winding length (m) of the support and the linear expansion coefficient (/°C) of the winding core in the circumferential direction are defined as D, L and α, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a magnetic recording medium and a magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium and a magnetic recording medium that can prevent the magnetic recording medium from being deformed by the influence of heat treatment during manufacturing.

  FIG. 4 is a diagram for explaining the manufacturing process of the magnetic recording medium. As shown in FIG. 4A, a belt-like support 51 is transported from an original roll, and a magnetic layer is applied to one surface of the support 51 by a magnetic layer application member 42 in an application unit 41. The back coat layer is applied to the other surface. Then, the support body 51 coated with the magnetic layer is wound around the support body winding portion 43. Next, as shown in FIG. 4B, the support body 51 is sent out from the support body winding section 43 to the calendar section 45, and is conveyed between a plurality of calendar rolls 44 provided in the calendar section 45. At this time, the smoothness of the surface of the magnetic layer in the support 51 is improved by passing the support 51 through the nip between the calendar rolls 44. And the support body 51 is wound around the core 52, and the support body roll 46 is formed (for example, refer patent document 1 and 2 below). Thereafter, as shown in FIG. 4 (c), the support roll 46 is left for 30 to 50 hours in an environmental atmosphere 47 set at a predetermined temperature (conventionally in a range of about 60 ° C. to 70 ° C.). A heat treatment step is performed. Here, for example, when manufacturing a magnetic tape, a magnetic tape having a predetermined tape width is manufactured by slitting the heat-treated support roll 46 in the longitudinal direction by a slitter in a cutting step.

JP 2000-285445 A JP-A-6-295436

  However, in the conventional method of manufacturing a magnetic recording medium, the heat treatment shown in FIG. 4C causes thermal contraction of the support roll 46 and the core 52 is thermally expanded, and the support roll 46 is wound and overlapped. Between them, the surface of the magnetic layer smoothed by the calender process is deformed by being pressed against the rough back coat layer due to the stress caused by the thermal contraction of the support 51 and the thermal expansion of the core 52, The surface roughness (Ra) sometimes increased. The increase in surface roughness (Ra) is significant on the core side, and becomes stronger as the number of turns (number of turns) increases. The difference in center of surface roughness (Ra) has caused a difference in center of the magnetic tape such as an error.

  Further, due to the heat shrinkage in the heat treatment step, deformation or wrinkles along the circumferential direction called cylindrical buckling as shown in FIG. 5 or the support rule shown in FIG. As in 56, deformation or wrinkles along the axial direction S called cinching may occur. If cylindrical buckling or cinching occurs in the support roll 46, output fluctuations occur, and the width dimension accuracy of the magnetic tape slit in the cutting process decreases, and the head cannot follow during servo signal recording or reproduction. It will cause a tracking error.

  Furthermore, if the thermal expansion of the core is large, the thickness unevenness of the original fabric is likely to occur due to heat treatment, and the dynamic curvature of the magnetic tape increases, or the polarity (direction) of the static curvature changes during the process. . As a result, there is a concern that the winding shape when the magnetic tape is wound around the tape reel may be deteriorated or the edge damage of the magnetic tape may be caused.

  For this reason, conventionally, when the support roll 46 is subjected to heat treatment, it is possible to prevent thermal expansion from occurring in the core, and to prevent the surface roughness Ra of the support from increasing or deforming. It was hoped to do.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the deformation of the support roll in the manufacturing process, to make the quality of the product uniform and to improve the quality, and to produce the magnetic recording medium. It is to provide a recording medium.

The above object of the present invention is achieved by the following configurations.
(1) When forming a support roll by winding the support around a core, the outer diameter (mm) of the core is D, the winding length (m) of the support is L, A method of manufacturing a magnetic recording medium, wherein a relationship of 200 ≧ 54000 / D + 0.007L + 10 ⁶ α is established, where α is a coefficient of linear expansion (/ ° C.) in the circumferential direction.
(2) The above-mentioned winding core is made of a material whose linear expansion coefficient in the circumferential direction is 5 × 10 ⁻⁶ or less and whose Young's modulus in the circumferential direction is 8000 kg / mm ² or more. A method for producing a magnetic recording medium according to 1).
(3) The method for manufacturing a magnetic recording medium according to (1) or (2) above, wherein the material of the winding core is CFRP.
(4) The method for manufacturing a magnetic recording medium according to any one of (1) to (3), wherein the support roll is heat-treated in an environmental atmosphere having a temperature of 50 ° C. or higher.
(5) A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to any one of (1) to (4) above.

  According to the present invention, there is no influence of the expansion of the core in the manufacturing process, and it is possible to prevent excessive stress from being generated on the support roll, the magnetic layer is pressed against the backcoat layer, and the surface of the magnetic layer is An increase in surface roughness (Ra) can be prevented, and the quality can be made uniform. In addition, when CFRP is used as the material for the core, the stress applied to the support due to the expansion and thermal contraction of the core in the heat treatment process is reduced, and the linearity of the tape is reduced when the magnetic tape is manufactured. It is possible to prevent a tracking error from occurring without lowering. Furthermore, it is possible to achieve a low heat shrinkage rate, to prevent the occurrence of cylindrical buckling and cinching of the support, and to prevent deterioration of the winding shape when the manufactured magnetic tape is wound. Quality and yield.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The method of manufacturing a magnetic recording medium according to this embodiment includes a step of coating and forming a magnetic layer containing a ferromagnetic powder and a binder on one surface of a long support, and a back coat on the other surface of the support. A coating process for coating and forming a layer; a calendar process for calendering the support on which the magnetic layer and the backcoat layer are formed; a heat treatment process for heat treating the calendered support; and a calendered support. A cutting step of slitting in the longitudinal direction. A servo process may be provided after the cutting process. In the present embodiment, the coating process and the calendar process can be performed according to a conventional manufacturing method.

  FIG. 1 is a diagram illustrating a state in which a calendar-treated support is wound around a winding core. FIG. 2 is a view showing a core around which the support of FIG. 1 is wound. As shown in FIG. 1, the support body B that has been calendered by the calendar roll 12 in the calendar process is wound around the outer peripheral surface of a cylindrical core 11 to form the support body roll 10.

  As shown in FIG. 2, the winding core 11 has a cylindrical main body, and the support body roll is comprised by making the support body B overlap and wind on the surrounding surface of this main body. The core 11 is provided with a shaft support portion for supporting the rotation in the circumferential direction extending in the axial direction on the side plates at both ends. The structure of the winding core does not matter. For example, reinforcement such as a rib may be provided inside the winding core, and the cylindrical portion may have a double structure.

  In the present embodiment, the outer diameter D of the core 11 is 400 mm or more, and the thickness t of the support B is 5 μm or more. Here, the thickness t of the support B is t when the number of times the support B is wound around the core 11 is n and the thickness of the entire support B wound around the core 11 is T. = T / n. Further, when the length of the support B wound around the core 11 is L, 1000 m ≦ L ≦ 12000 m is set, but the length L of the support is not limited to this range.

Furthermore, in this embodiment, carbon fiber (CFRP) was used as a material constituting the core 11. Here, as the material of the winding core 11, a material having a linear expansion coefficient α (/ ° C.) of 5 × 10 ⁻⁶ or less can be used, for example, a LEX material (registered trademark of Nippon Casting Co., Ltd.) can be used. .
When the core 11 is made of the above material, it is preferable that both the body and the side plate are made of the same material in order to suppress thermal deformation due to the linear expansion coefficient. Further, the outer peripheral low thermal expansion material portion may be a removable sleeve. Further, the outer shape may be a cylindrical shape or a crown shape of 50 μm / R. The material of the winding core is preferably set to a Young's modulus of 8000 kg / mm ² or more in order to efficiently exclude entrained air during winding and prevent cylindrical buckling.

The inventor sets the relationship of 200 ≧ 54000 / D + 0.007L + 10 ⁶ α to be satisfied, so that when the support B is subjected to the heat treatment step, the thermal expansion of the core 11 is reduced and the support is supported. It has been found that the stress due to thermal contraction of the body B can be suppressed to a low level and the magnetic layer of the support B can be prevented from being pressed against the backcoat layer. By doing so, it is possible to prevent the surface roughness (Ra) of the magnetic layer surface from increasing.

In addition, when the inventor performs heat treatment on the support roll 10 by forming the core 11 with a material having a linear expansion coefficient of 5 × 10 ⁻⁶ or less and a Young's modulus of 8000 kg / mm ² or more, It has been found that cylindrical buckling and cinching can be prevented. If this happens, output fluctuations will occur during playback, the width dimension accuracy of the magnetic tape slit in the cutting process will decrease, and tracking errors may occur because the head cannot follow during servo signal recording or playback. Can be prevented.

  FIG. 3 is a diagram showing a heat treatment step of the support roll of this embodiment. In the heat treatment step of this embodiment, the support roll 10 was heat treated with the temperature of the environmental atmosphere 21 set to 50 ° C. or higher. Here, the temperature of the environmental atmosphere 21 is preferably in the range of 50 ° C. to 120 ° C., and the heat treatment is preferably performed in the range of 1 hour to 50 hours.

  The magnetic recording medium obtained by the method for manufacturing a magnetic recording medium according to the present invention is, for example, a magnetic tape. The field of application of the magnetic tape is not particularly limited. For example, the effect can be obtained by using the magnetic tape for a magnetic tape cartridge used for backup of computer data.

  The magnetic tape basically means a magnetic tape having a magnetic layer on one side of a support and a back coat layer on the other side of the support. For example, the support, the magnetic layer, A magnetic tape having a structure in which a nonmagnetic layer is further provided between them may be used.

  As the support, those conventionally used as a support material for magnetic tape can be used, and a non-magnetic one is particularly preferable. Examples of these are polyesters (eg, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), mixtures of polyethylene terephthalate and polyethylene naphthalate, polymers containing an ethylene terephthalate component and an ethylene naphthalate component), polyolefins (Eg, polypropylene), cellulose derivatives (eg, cellulose diacetate, cellulose triacetate), polycarbonate, polyamide (especially aromatic polyamide, aramid), polyimide (especially wholly aromatic polyimide), and other synthetic resin films. . Among these, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aromatic polyamide, and aramid are preferable. The thickness of the support is not particularly limited, but is preferably in the range of 2 to 8 μm (more preferably 3 to 8 μm, particularly preferably 3 to 7 μm).

The magnetic layer is basically made of a ferromagnetic powder and a binder. The magnetic layer usually further contains a lubricant, carbon black as a conductive powder, and an abrasive. Examples of the ferromagnetic powder include γ-Fe ₂ O ₃ , Fe ₃ O ₄ , FeOx (x = 1.33 to 1.5), CrO ₂ , Co-containing γ-Fe ₂ O ₃ , and Co-containing FeOx (x = 1.33-1.5), ferromagnetic metal powder, and plate-shaped hexagonal ferrite powder. In the present invention, it is preferable to use a ferromagnetic metal powder or a plate-shaped hexagonal ferrite powder as the ferromagnetic powder. Particularly preferred is a ferromagnetic metal powder.

The ferromagnetic metal powder preferably has a specific surface area of 30 to 70 m ² / g, and a crystallite size determined by an X-ray diffraction method is 50 to 300A. If the specific surface area is too small, it will not be possible to sufficiently cope with high density recording, and if it is too large, it will not be possible to disperse sufficiently, so that it will not be possible to form a smooth magnetic layer, and thus it will not be able to cope with high density recording. The ferromagnetic metal powder is required to contain at least Fe, and specifically, a simple metal or an alloy mainly composed of Fe, Fe—Co, Fe—Ni, Fe—Zn—Ni, or Fe—Ni—Co. It is. As for the magnetic properties of these ferromagnetic metal powders, the saturation magnetization (σs) is 110 emu / g or more, preferably 120 emu / g or more and 170 emu / g or less in order to achieve a high recording density. The coercive force (Hc) is in the range of 800 to 3000 oersted (Oe) (preferably 1500 to 2500 Oe). And the long axis length (namely, average particle diameter) of the powder calculated | required with a transmission electron microscope is 0.5 micrometer or less, Preferably, it is 0.01-0.3 micrometer, and an axial ratio (long axis length / short axis length, The needle ratio) is 5 or more and 20 or less, preferably 5-15. In order to further improve the characteristics, non-metals such as B, C, Al, Si and P, or salts and oxides thereof may be added during the composition. Usually, an oxide layer is formed on the particle surface of the metal powder in order to stabilize it chemically.

The plate-like hexagonal ferrite powder has a specific surface area of 25 to 65 m ² / g, a plate-like ratio (plate diameter / plate thickness) of 2 to 15, and a plate diameter of 0.02 to 1.0 μm. . The plate-shaped hexagonal ferrite powder is difficult to record at high density if the particle size is too large or too small for the same reason as the ferromagnetic metal powder. The plate-shaped hexagonal ferrite is a ferromagnetic material having a flat plate shape and an easy axis of magnetization in a direction perpendicular to the flat plate surface, specifically, barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and the like. The cobalt substitution product of these can be mentioned. Of these, cobalt substitutes of barium ferrite and cobalt substitutes of strontium ferrite are particularly preferable. To the plate-shaped hexagonal ferrite used in the present invention, elements such as In, Zn, Ge, Nb, and V may be added as necessary to improve the characteristics. Regarding the magnetic properties of these plate-shaped hexagonal ferrite powders, in order to achieve a high recording density, the particle size as described above is required and at the same time, the saturation magnetization (σs) is at least 50 emu / g or more, preferably It is 53 emu / g or more. The coercive force is in the range of 700 to 2000 Oersted (Oe), and preferably in the range of 900 to 1600 Oe.

The water content of the ferromagnetic powder is preferably 0.01 to 2% by weight. It is preferable to optimize the water content depending on the type of the binder. The pH of the ferromagnetic powder is preferably optimized depending on the combination with the binder used, and the pH is usually in the range of 4 to 12, preferably in the range of 5 to 10. The ferromagnetic powder may be subjected to surface treatment with Al, Si, P, or an oxide thereof as required. The amount used in the surface treatment is usually 0.1 to 10% by weight with respect to the ferromagnetic powder. By performing the surface treatment, adsorption of a lubricant such as a fatty acid can be suppressed to 100 mg / m ² or less. The ferromagnetic powder may contain soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr. However, if the content is 5000 ppm or less, the properties are not affected.

  The lubricant is added to ooze out on the surface of the magnetic layer, thereby relaxing the friction between the magnetic layer surface and the magnetic head, the guide pole of the drive and the cylinder, and smoothly maintaining the sliding contact state. Examples of the lubricant include fatty acids or fatty acid esters. Examples of fatty acids include acetic acid, propionic acid, octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid, arachic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, And aliphatic carboxylic acids such as palmitoleic acid or mixtures thereof.

  Examples of fatty acid esters include butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, 2-hexyl decyl stearate, Acylation of butyl palmitate, 2-ethylhexyl myristate, butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether with stearic acid , Diethylene glycol dipalmitate, hexamethylenediol acylated with myristic acid to give a diol, and various ester compounds such as glycerin oleate be able to. These can be used alone or in combination. The normal content of the lubricant is in the range of 0.2 to 20 parts by weight (preferably 0.5 to 10 parts by weight) with respect to 100 parts by weight of the ferromagnetic powder of the magnetic layer.

Carbon black, reduce the surface electric resistance of the magnetic layer (Rs), reduction of the dynamic friction coefficient (mu _K value), improvement of running durability, and added a variety of purposes, such as to ensure a smooth surface of the magnetic layer Is done. Carbon black preferably has an average particle size in the range of 3 to 350 nm (more preferably 10 to 300 nm). The specific surface area is preferably 5 to 500 m ² / g (more preferably 50 to 300 m ² / g). The DBP oil absorption is preferably in the range of 10 to 1000 mL / 100 g (more preferably 50 to 300 mL / 100 g). The pH is preferably 2 to 10, the water content is preferably 0.1 to 10%, and the tap density is preferably 0.1 to 1 g / cc.

  Carbon black obtained by various manufacturing methods can be used. Examples of carbon black that can be used include furnace black, thermal black, acetylene black, channel black, and lamp black. Specific examples of carbon black products include BLACKPEARLS 2000, 1300, 1000, 900, 800, 700, VULCANXC-72 (manufactured by Cabot Corporation), # 35, # 50, # 55, # 60 and # 60. 80 (above, manufactured by Asahi Carbon Co., Ltd.), # 3950B, # 3750B, # 3250B, # 2400B, # 2300B, # 1000, # 900, # 40, # 30, and # 10B (above, Mitsubishi Chemical ( ), CONDUCTEXSC, RAVEN150, 50, 40, 15 (above, Columbia Carbon Co., Ltd.), Ketjen Black EC, Ketjen Black ECDJ-500, and Ketjen Black ECDJ-600 (above, Lion Exo Co., Ltd.) Manufactured). The usual addition amount of carbon black is 0.1 to 30 parts by weight, preferably 0.2 to 15 parts by weight with respect to 100 parts by weight of the ferromagnetic powder.

Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr ₂ 0 ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). These abrasives preferably have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle size of 0.05 to 1 μm (more preferably 0.2 to 0.8 μm). . The addition amount of the abrasive is usually in the range of 3 to 25 parts by weight (preferably 3 to 20 parts by weight) with respect to 100 parts by weight of the ferromagnetic powder.

  Examples of the binder for the magnetic layer include thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl A polymer or a copolymer containing acetal and vinyl ether as structural units can be given. Examples of the copolymer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate ester-acrylonitrile copolymer, acrylate ester-vinylidene chloride copolymer. Polymer, Acrylate ester-Styrene copolymer, Methacrylate ester-Acrylonitrile copolymer, Methacrylate ester-Vinylidene chloride copolymer, Methacrylate ester-Styrene copolymer, Vinylidene chloride-Acrylonitrile copolymer , Butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, and chlorovinyl ether-acrylic ester copolymer.

  In addition to the above, polyamide resin, fiber-based resin (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resin, polyurethane resin, various rubber resins, etc. are also used. can do.

  Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, acrylic reactive resins, formaldehyde resins, silicone resins, epoxy-polyamide resins, Mention may be made of a mixture of polyester resin and polyisocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, and a mixture of polyurethane and polyisocyanate.

  Examples of the polyisocyanate include tolylene diisocyanate, 4-4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, and the like. Isocyanates, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates.

  As the polyurethane resin, known resins having structures such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used.

  In the present invention, the binder of the magnetic layer is vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, and A combination of at least one resin selected from nitrocellulose and a polyurethane resin, or a combination of these with a polyisocyanate is preferable.

As the binder, as necessary to obtain the durability of the layer obtained more excellent _{dispersibility, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, -O _{-P = O (OM) 2 (} M represents a hydrogen atom or an alkali metal salt,.), - OH, -NR 2, -N + R 3 (R is a hydrocarbon group.), an epoxy group, - It is preferable to use at least one polar group selected from SH, —CN and the like by copolymerization or addition reaction. Such polar groups are preferably introduced into the binder in an amount of 10 ^-1 to 10 ^-8 mol / g (more preferably 10 ^-2 to 10 ^-6 mol / g).

  The binder for the magnetic layer is usually used in the range of 5 to 50 parts by weight (preferably 10 to 30 parts by weight) with respect to 100 parts by weight of the ferromagnetic powder. When a combination of vinyl chloride resin, polyurethane resin, and polyisocyanate is used as a binder in the magnetic layer, the vinyl chloride resin is 5 to 70% by weight and the polyurethane resin is 2 to 50% by weight in the total binder. % And polyisocyanates are preferably used in amounts ranging from 2 to 50% by weight.

  A dispersing agent can be added to the coating solution for forming the magnetic layer of the magnetic tape in order to favorably disperse the magnetic powder in the binder. Further, if necessary, conductive particles (antistatic agent) other than plasticizer, carbon black, antifungal agent and the like can be added. Examples of the dispersant include 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and stearic acid. A fatty acid (RCOOH, R is an alkyl group having 11 to 17 carbon atoms, or an alkenyl group), a metal soap composed of an alkali metal or an alkaline earth metal of the fatty acid, a compound containing fluorine of the fatty acid ester, Fatty acid amide, polyalkylene oxide alkyl phosphate ester, lecithin, trialkyl polyolefinoxy quaternary ammonium salt (alkyl is 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.), sulfate, copper phthalocyanine, etc. Can be used. These may be used alone or in combination. The dispersant is usually added in the range of 0.5 to 20 parts by weight with respect to 100 parts by weight of the binder of the magnetic layer.

  Next, the back coat layer will be described. The back coat layer is preferably formed of carbon black and a binder. It is preferable that an inorganic powder or a lubricant is further added. It is preferable to use a combination of two types of carbon black having different average particle sizes. In this case, it is preferable to use a combination of fine particle carbon black having an average particle size of 10 to 20 nm and coarse particle carbon black having an average particle size of 230 to 300 nm. In general, by adding fine carbon black as described above, the surface electrical resistance of the backcoat layer can be set low, and the light transmittance can also be set low. Some magnetic recording devices utilize the light transmittance of the tape and are used for the operation signal. In such a case, the addition of particulate carbon black is particularly effective. In addition, particulate carbon black is generally excellent in retention of liquid lubricants, and contributes to reduction of the friction coefficient when used in combination with lubricants. On the other hand, the coarse particulate carbon black having a particle size of 230 to 300 nm has a function as a solid lubricant, and forms fine protrusions on the surface of the back layer, reducing the contact area, and reducing the friction coefficient. Contributes to reduction.

  Specific products of the particulate carbon black include the following. RAVEN2000B (18 nm), RAVEN1500B (17 nm) (above, manufactured by Columbia Carbon Co., Ltd.), BP800 (17 nm) (manufactured by Cabot), PRINTEX90 (14 nm), PRINTEX95 (15 nm), PRINTEX85 (16 nm), PRINTEX75 (17 nm) (and above) Degussa), # 3950 (16 nm) (Mitsubishi Chemical Corporation). Examples of specific products of coarse particulate carbon black include thermal black (270 nm) (manufactured by Kerncarb) and Ravenmtp (275 nm) (manufactured by Columbia Carbon).

  When two types of backcoat layers having different average particle sizes are used, the content ratio (weight ratio) of fine particle carbon black of 10 to 20 nm and coarse particle carbon black of 230 to 300 nm is the former: latter = It is preferably in the range of 98: 2 to 75:25, and more preferably in the range of 95: 5 to 85:15. The content of carbon black (the total amount thereof) in the back coat layer is usually in the range of 30 to 110 parts by weight, preferably in the range of 50 to 90 parts by weight with respect to 100 parts by weight of the binder.

  It is preferable to use two types of inorganic powders having different hardnesses. Specifically, it is preferable to use a soft inorganic powder having a Mohs hardness of 3 to 4.5 and a hard inorganic powder having a Mohs hardness of 5 to 9. By adding a soft inorganic powder having a Mohs hardness of 3 to 4.5, the friction coefficient can be stabilized by repeated running. Moreover, when the hardness is within this range, the sliding guide pole is not scraped. The average particle size of the soft inorganic powder is preferably in the range of 30 to 50 nm. Examples of the soft inorganic powder having a Mohs hardness of 3 to 4.5 include calcium sulfate, calcium carbonate, calcium silicate, barium sulfate, magnesium carbonate, zinc carbonate, and zinc oxide. These can be used alone or in combination of two or more. Among these, calcium carbonate is particularly preferable. The content of the soft inorganic powder in the backcoat layer is preferably in the range of 10 to 140 parts by weight, more preferably in the range of 35 to 100 parts by weight with respect to 100 parts by weight of the carbon black.

  By adding a hard inorganic powder having a Mohs hardness of 5 to 9, the strength of the backcoat layer is enhanced and the running durability is improved. When this is used together with carbon black, there is little deterioration even with repeated sliding, and a strong backcoat layer is obtained. In addition, the addition of the inorganic powder provides an appropriate polishing force and reduces the adhesion of shavings to the tape guide pole and the like. The hard inorganic powder preferably has an average particle size in the range of 80 to 250 nm (more preferably, 100 to 210 nm).

Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These powders may be used alone or in combination. Among these, α-iron oxide or α-alumina is preferable. The content of the hard inorganic powder is usually in the range of 3 to 30 parts by weight, preferably in the range of 3 to 20 parts by weight with respect to 100 parts by weight of the carbon black.

  The back coat layer can contain a lubricant. The lubricant can be appropriately selected from the lubricants described in the magnetic layer. In the backcoat layer, the lubricant is usually added in the range of 1 to 5 parts by weight with respect to 100 parts by weight of the binder. Moreover, the dispersing agent described in the magnetic layer can also be added to the backcoat layer. The amount of the dispersant added can be the same as the amount added to the magnetic layer.

  As the binder for the backcoat layer, the binder described in the magnetic layer can be used. Binders that can be used include nitrocellulose resins, polyurethane resins, polyester resins, and polyisocyanates as curing agents. The binder of the backcoat layer is usually 5 to 250 parts by weight (preferably 10 to 200 parts by weight) with respect to 100 parts by weight of carbon black.

  The magnetic tape of the present invention may have a configuration in which a nonmagnetic layer is further provided between the support and the magnetic layer. That is, a magnetic tape having a nonmagnetic layer and a magnetic layer in this order on one side of the support and a backcoat layer on the other side of the support may be used. The nonmagnetic layer is a substantially nonmagnetic layer containing a nonmagnetic powder and a binder. This non-magnetic layer needs to be substantially non-magnetic so as not to affect the electromagnetic conversion characteristics of the magnetic layer on the non-magnetic layer, but is small enough not to affect the electromagnetic conversion characteristics of the magnetic layer. Even if the magnetic powder is contained, there is no particular problem. Usually, the nonmagnetic layer contains a lubricant in addition to these components.

  Examples of the nonmagnetic powder used in the nonmagnetic layer include a nonmagnetic inorganic powder and carbon black. The non-magnetic inorganic powder is preferably relatively hard, and preferably has a Mohs hardness of 5 or more (more preferably 6 or more). Examples of nonmagnetic inorganic powders include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium dioxide, silicon dioxide, Mention may be made of boron nitride, zinc oxide, calcium carbonate, calcium sulfate and barium sulfate. These can be used alone or in combination. Of these, titanium dioxide, α-alumina, α-iron oxide, or chromium oxide is preferable. The average particle diameter of the nonmagnetic inorganic powder is preferably in the range of 0.01 to 1.0 μm (preferably 0.01 to 0.5 μm, particularly 0.02 to 0.1 μm).

  Carbon black is added for the purpose of imparting electrical conductivity to the magnetic layer to prevent electrification and ensuring the smooth surface properties of the magnetic layer formed on the nonmagnetic layer. As the carbon black used in the nonmagnetic layer, the carbon black described in the magnetic layer can be used. However, the carbon black used in the nonmagnetic layer preferably has an average particle size of 35 nm or less (more preferably 10 to 35 nm). The normal addition amount of carbon black is 3 to 20 parts by weight, preferably 4 to 18 parts by weight, and more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the total nonmagnetic inorganic powder in the nonmagnetic layer. Part.

  As the lubricant, the fatty acid or fatty acid ester described in the magnetic layer can be used. The addition amount of the lubricant is usually in the range of 0.2 to 20 parts by weight with respect to 100 parts by weight of the total nonmagnetic powder of the nonmagnetic layer.

  As the binder for the nonmagnetic layer, the binders described for the magnetic layer described above can be used. The binder is usually used in the range of 5 to 50 parts by weight (preferably 10 to 30 parts by weight) with respect to 100 parts by weight of the nonmagnetic powder of the nonmagnetic layer. In the case of using a combination of vinyl chloride resin, polyurethane resin, and polyisocyanate as binders in the nonmagnetic layer, 5 to 70% by weight of vinyl chloride resin and 2 to 50 polyurethane resin in all binders. It is preferred to use such that the polyisocyanate is included in an amount ranging from 2% to 50% by weight. In the nonmagnetic layer, an optional component that can be added to the magnetic layer may be added.

  The magnetic tape of the present invention is prepared for a magnetic layer after preparing a coating solution for forming a magnetic layer (a magnetic layer and a nonmagnetic layer in the case where a nonmagnetic layer is provided) and a backcoat layer. The coating liquid for coating is formed on one side of the long support web and the coating liquid for the backcoat layer on the other side according to the conventional method, and dried to obtain a long magnetic recording web. Can do. Thereafter, the web is calendered, and subsequently slitted in the length direction to obtain a magnetic tape having a desired width, and then the magnetic layer surface is slid with the above-mentioned molded body in accordance with the present invention. By performing this, a magnetic tape can be manufactured.

  In the case of a magnetic tape having a non-magnetic layer, the method for forming the magnetic layer and the non-magnetic layer is not particularly limited, but the magnetic layer is a coating formed after applying the non-magnetic layer coating liquid on the support. It is preferably formed by using a so-called wet-on-wet coating method in which a magnetic layer coating solution is applied to a layer (nonmagnetic layer) while it is in a wet state.

Examples of the application method by the wet-on-wet method include the following methods.
(1) Using a gravure coating, roll coating, blade coating, or extrusion coating apparatus, a nonmagnetic layer is first formed on a support, and while the nonmagnetic layer is in a wet state, the support pressurization type ext A method of forming a magnetic layer with a roux coating device (see Japanese Patent Laid-Open Nos. 60-238179, 1-46186, and 2-265672).
(2) A method in which a magnetic layer and a nonmagnetic layer are formed almost simultaneously on a support using a coating apparatus comprising a single coating head having two coating liquid slits (Japanese Patent Laid-Open No. 63-88080, (See JP-A-2-17921 and JP-A-2-265672).
(3) A method in which a magnetic layer and a nonmagnetic layer are formed almost simultaneously on a support using an extrusion coating apparatus with a backup roller (see JP-A-2-174965). The nonmagnetic layer and the magnetic layer are preferably formed using a simultaneous multilayer coating method.

  The surface of the back coat layer of the magnetic tape tends to be transferred to the surface of the magnetic layer while the tape is wound. For this reason, it is preferable that the surface of the back coat layer also has relatively high smoothness. The surface of the back coat layer of the magnetic tape is preferably adjusted so that its surface roughness Ra (centerline average roughness with a cutoff of 0.08 mm) is in the range of 0.003 to 0.060 μm. . The surface roughness can be adjusted by the material of the calendar roll used, its surface properties, pressure, etc., in the surface treatment process using a calendar, usually after the formation of the coating film.

  The magnetic layer of a magnetic tape having a single-layer structure having a magnetic layer on one side of the support and a backcoat layer on the other side, manufactured according to the manufacturing method of the present invention, has a thickness of 1.0 to 3 It is preferably in the range of 0.0 μm (more preferably, 1.5 to 2.5 μm). The total thickness of the magnetic tape having this configuration is preferably in the range of 4.0 to 12.0 μm, more preferably 4.0 to 10.0 μm. The thickness of the back coat layer is preferably in the range of 0.1 to 1.0 μm (more preferably 0.2 to 0.8 μm).

  The magnetic layer of the magnetic tape having a nonmagnetic layer preferably has a thickness in the range of 0.01 to 1.0 μm (more preferably 0.05 to 0.5 μm). The thickness of the nonmagnetic layer is preferably in the range of 0.01 to 3.0 μm (more preferably 0.5 to 2.5 μm). The ratio of the thickness of the magnetic layer to the thickness of the nonmagnetic layer is preferably in the range of 1: 2 to 1:15 (more preferably 1: 5 to 1:12). The total thickness of the magnetic tape having the nonmagnetic layer and the thickness of the backcoat layer are preferably in the same range as the magnetic tape having the single layer structure.

Examples and comparative examples will be compared and examined by the following tests to explain the effects of the configuration of the present invention.
In this test, a support having a thickness of 9 μm on which a magnetic layer was formed was wound on a core shown in Table 1 below, and a magnetic tape (slit support) serving as a sample was prepared under the same conditions and steps. A test was conducted to check whether or not dropout (DO) occurred by following a magnetic recording head (not shown) with respect to these magnetic tapes. Here, a value obtained by the equation of 54000 / D + 0.007L + 10 ⁶ α is defined as a P value. Here, the P value is an index indicating the strength of winding the support.

In this test, any one of 300 mm, 400 mm, and 480 mm in diameter was used as the winding core, and any of aluminum (Al) and CFRP was used as the material. Further, as the core, either one having a linear expansion coefficient of 2.30 × 10 ⁻⁵ or 2.00 × 10 ⁻⁶ was used. Further, the length of the support wound on the core (the treatment length in Table 1) was 4000 m, 8000 m, or 12000 m. In this test, those in which dropout occurred were indicated by x, and those in which dropout did not occur were indicated by ◯. The results are shown in Table 1.

  As shown in Table 1, a magnetic tape in which dropout of the magnetic tape occurred in the support roll having a P value exceeding 200, but no dropout occurred in the support roll having a P value of 200 or less was obtained.

It is a figure explaining the state which is making the support body wind around a core. It is a figure which shows the winding core by which the support body of FIG. 1 is wound. It is a figure which shows the heat processing process of the support body roll of this embodiment. It is a figure explaining the manufacturing process of a magnetic recording medium. It is a figure explaining the state which cylindrical buckling produced in the support body roll. It is a figure explaining the state which the cinch produced in the support body roll.

Explanation of symbols

10 support roll 11 core B support D outer diameter of core

Claims (5)

When the support roll is formed by winding the support around the core, the outer diameter (mm) of the core is D, the winding length (m) of the support is L, and the circumferential direction of the core A method of manufacturing a magnetic recording medium, wherein a relationship of 200 ≧ 54000 / D + 0.007L + 10 ⁶ α is established, where α is a linear expansion coefficient (/ ° C.). 2. The core according to claim 1, wherein the core is made of a material having a linear expansion coefficient of 5 × 10 ⁻⁶ or less in the circumferential direction and a Young's modulus in the circumferential direction of 8000 kg / mm ² or more. Manufacturing method of magnetic recording medium.   3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the material of the winding core is CFRP.   The method of manufacturing a magnetic recording medium according to claim 1, wherein the support roll is heat-treated in an environmental atmosphere having a temperature of 50 ° C. or higher.   A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to claim 1.

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